Cellular telephones typically include several parts that must be assembled within front and base shells or covers. These parts include the display, the keypad, a light guide for distributing light to the display and keypad, and a printed circuit board that contains the telephone's electronics. In addition, a telephone generally includes other components such as a microphone and speaker.
Assembly of such a telephone can be difficult because of the small size and delicate nature of the parts, and because of the relative position and orientation in which the parts must be assembled.
The present invention provides a method of assembling a cellular telephone that facilitates the assembly process. The method of assembly of the invention permits the formation of subassemblies of the parts, which may then be more easily handled for further assembly or processing prior to final assembly.
The present invention also provides a cellular telephone having a light guide that facilitates the alignment and fastening of the front and base shell of the telephone. The light guide according to the invention includes a mounting hole positioned in a central region of the light guide and a locating hole positioned remote from the mounting hole. Pins in the front and base shells are aligned with the mounting hole and locating hole to facilitate assembly of the shells.
Alternatively, a mounting pin and locating pin may be provided in only one of the front shell and the base shell, the pins having sufficient length to extend through the components that form a subassembly, as further described below.
The mounting boss and locating hole in the light guide, and, correspondingly, the mounting pins and location pins in the front shell and rear shell are located to facilitate the alignment f unction. Preferably, the mounting boss and mounting pins are formed a central portion of the light guide and shells, respectively, and the locating hole and locating pins are formed near an edge of the light guide and shells.
According to another aspect of the invention, the pins in the front and rear shells that mate with the mounting hole of the light guide are shaped for securable engagement with the mounting hole for fastening of the light guide and front and rear shells. The pins and the mounting hole may be shaped for a force fit, for frictional engagement, or with a detent and mating groove, for example.
According to the method of the invention, a front shell subassembly may be formed by placing a keypad having a plurality of keys in a front shell with the keys extending through keyhole in the front shell, positioning the light guide in the front shell, fastening the light guide to the front shell by frictionally engaging a mounting pin on the front shell with a mounting hole in the light guide, and inserting a locating pin on the front shell in a locating hole in the light guide.
According to another aspect of the method, the base shell may be fastened to the front shell subassembly by the steps of aligning the base shell with the front shell by positioning a base shell mounting pin with the mounting hole in the light guide, and positioning a locating pin in the base shell with the locating hole in the light guide, and fastening the base shell to the front shell by frictionally engaging the base shell mounting pin in the mounting hole in the light guide.
The method in accordance with the invention further includes the step, before fastening the base shell to the front shell, of positioning a printed circuit board in the base shell by aligning holes in the printed circuit board with the mounting pin and locating pin of the base shell so that the pins extend through the holes in the printed circuit board.
According to another aspect of the invention, the light guide has a shape that improves the distribution of light to a display and keyboard, illuminating the display and keyboard in a more uniform manner that substantially eliminates dark and bright areas. The light guide of the invention more provides a light source coupling to receive and transmit light more efficiently into the light guide, thus, more effectively distribute light throughout the light guide. Accordingly, a light guide of the invention provides a brighter display and keys, and may require fewer light sources than conventional light guides. The light guide may thus saves manufacturing expense and time, component cost, and reduces battery energy consumption in the completed device.
According to the invention, the light guide comprises an element formed of a translucent material having an upper surface, a lower surface and a peripheral edge. The element is preferably a planar, rectangular component shaped to correspond to the keyboard and display of a telephone.
According to the invention, a plurality of light coupling recesses is provided on the peripheral edge to transmit light into the light guide. The light coupling recesses are preferably arcuately shaped, and more preferably semicircular. This feature helps to guide light from light sources uniformly into the light guide, thus avoiding bright and dark regions. In a preferred embodiment of the invention, the light coupling recesses are positioned on one side of the light guide in equally spaced relationship. In this way, a maximum amount of useful light is transmitted to illuminate a desired portion of the light guide, for example, that portion serving as a display screen backing. Alternatively, the light coupling recesses may be positioned as convenient around the periphery of the light guide for a desired illumination pattern.
According to another aspect of the invention, a plurality of reflecting recesses are provided on the peripheral edge of the light guide to reflect light striking the edge toward the key holes. According to a preferred embodiment of the invention, the reflecting recesses are positioned between adjacent keys hole locations. The reflecting recesses may be arcuately shaped or formed with two or more facets. According to a preferred embodiment, the reflecting recesses are V-shaped.
According to yet another aspect of the invention, the upper and lower surfaces of the element may be formed as glossy reflective surfaces, which facilitates the transmission of light through the light guide while minimizing the leakage of light from the surfaces.